Process of synthesis of 5-methoxy- 2-[(4-methoxy-3,5-dimethy-2-pyridyl)methyl]sulfiny-1h-benzimidazole

Abstract

An improved process of synthesis of 5-methoxy-2-[(4-methoxy-3,5-dimethyl-2-pyridyl)methyl]sulfinyl-1H-benzimidazole (omeprazole) by oxidation of 5-methoxy-2-[[(4-methoxy-3,5-dimethyl-2-pyridyl)methyl]thio]benzimidazole with 3-chloroperoxy-benzoic acid in ethyl acetate wherein omeprazole is poorly soluble, at a temperature between -10° C. and 5° C. is disclosed. The second step is a purification of the crude product by dissolution and reprecipitation of the final product.

Description

(C07D 401 / 12)The present invention relates to an improved process of synthesis of 5-methoxy-2-[(4-methoxy-3,5-dimethyl-2-pyridyl)methyl]sulfinyl-1H-benzimidazole (omeprazole) of the formula ##STR1##wherein 5-methoxy-2-[[(4-methoxy-3,5-dimethyl-2-pyridyl)methyl]thio]benzimidazole is reacted with 3-chloroperoxybenzoic acid in ethyl acetate, wherein the final product--omeprazole--is poorly soluble.Omeprazole is the first medicament from the group of formulations for controlling the secretion of gastric acid, from the group of proton pump inhibitors. Namely, it inhibits the enzyme H / K-ATPase (a proton pump) in a parietal cell and thus also inhibits the last phase of acid secretion.TECHNICAL PROBLEMThere is a constant need to prepare omeprazole of high purity in a simple and readily feasible way. In the literature processes of synthesis up to a crude omeprazole are disclosed; said omeprazole, however, contains by-products and hence it is not suitable for pharmaceutical use.PRIOR ART5-met...

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Benefits of technology

3-chlorobenzoic acid formed in oxidation is, due to the instability of omeprazole in acidic medium, the cause of omeprazole decomposition and therefore it is absolutely necessary that the acid formed and the final product are in contact for as short a period of time as possible. In hitherto known processes this problem has been solved by filtration or a simultaneous removal of 3-chlorobenzoic acid formed in oxidation by extraction into the alkaline aqueous phase, whereas the omeprazole formed remained in the organic phase. The isolation of the final product from a two-phase system, alkaline aqueous phase--organic phase, requires several steps (extraction of 3-chlorobenzoic acid from the organic phase into the alkaline aqueous phase, extraction of omeprazole with NaOH into the aqueous phase under pH control and temperature control, separation of the organic and aqueous phases, crystallization of omeprazole under pH control and filtration of the final product), which means a more sophisticated technological process.

The object of the invention is thus an improved process of the synthesis of omeprazole, wherein the effect of the acidic medium on omeprazole decomposition is reduced in such a way that as a solvent in the oxidation of 5-methoxy-2-[[(4-methoxy-3,5-dimethyl-2-pyridyl)methyl]thio]benzimidazole with 3-chloroperoxybenzoic acid ethyl acetate is used wherein the final product--omeprazole--is poorly soluble since omeprazole formed during the reaction is crystallized and the acid formed remains in the ethyl acetate solution. Hence, for the final isolation of the product only one step is necessary, i.e. the filtration of the product. Therefore the present invention is, with regard to technological feasibility, essentially more simple, more economical and faster.

Problems solved by technology

A disadvantage of the said process is also the fact that the pH of the aqueous phase over the reaction mixture has to be carefully monitored during the whole process.

At a greater amount of the catalyst there is also a risk of contamination of the final product with heavy metals.

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